Anaerobic digestion technology, i.e. CSTR, IC, UASB, EGSB, HIRAD , as a major and important process of environmental engineering, has been widely used in many areas like Municipal solid waste (MSW), waste water treatment plant (WWTP), sludge treatment, food waste, industrial waste water treatment and so on. The anaerobic digester structure can be egg-shaped digester, concrete tank, Lip tank, enamel assembling tank, or carbon steel welding tank and so on.
Biogas, as a by-product from anaerobic digestion, was once neglected and discharged to air freely, which cause odor problem and potential safety hazard of explosion. In recent years, the implementation of environmental protection law has been reinforced than ever. Especially in China, the government has proposed 'Green, Recycling, Low-carbon' policy to undertake the big challenge of the SMOG and PM2.5 problem all over China.
Biogas, is now recognized and utilized as 'Green Energy'. It can be simply burned by a flare, or utilized as green fuel of gas Boiler or CHP cogeneration, or upgraded to CNG quality and injected to gas grid or be as vehicle fuel!
A typical case study shows that the electricity generated by biogas covers 100% of the total electricity required by running a complete WWTP (Waste Water Treatment Plant). In this case, Environtec has provided a complete line of biogas treatment products including: Desulfurization, Double Membrane Gas Holder, Filter, Gas Booster, Flare and so on.
Each anaerobic tank can be installed a Gas Dome (MHD) on it for collecting the biogas. The gas dome has the function of inspection window, pressure sensor, liquid level detection, and also overpressure and negative pressure protection.
The biogas firstly goes through the Gravel Filter to remove solid particles. A lot of condensate water can be collected and discharged automatically. The pressure loss is normally 1-2mbar.
Biogas then enters the desulfurization system. According to the inlet H2S concentration of raw gas, different processes i.e.
Biological Desulfurization, Chemical Scrubber, Dry Type Desulfurization , and Active Carbon Filter can be chosen.
Biological Desulfurization, using microbial metabolic principle without consuming any chemicals, has proofed its low operating cost and the Best Practice Technology (BMP).
Biogas then goes to the gas holder for storage and pressure buffing. The design of storage time is normally 1-8 hours, and pressure is normally 10-20mbar. Double Membrane Gas Holder, in comparison with traditional steel tanks, avoids the steel corrosion problem and the freezing of water sealing problem in winter time. Therefore, DMG with its outstanding shape and outlook, quick and easy installation, low investment cost, has been proofed to be the Best Practice Technology (BMP).
Before it enters the end-user, biogas shall go through Ceramic Filter to reduce small particles to an accuracy of 3-8um. According to engineering and design requirements, Biogas Booster can be chosen to increase the gas pressure. Biogas Chiller can be also necessary to reach the Relative Humidity requirement (RH 80%) for gas boiler, or gas generator.
Biogas Flare, as an emergency safety device, which is necessary for burning excessive biogas. Flare is controlled by gas holder signal and/or pipe pressure signal automatically. Biogas flare is always designed with concealed flame type, which means no flame is visible from outside for safety purpose.